Ensure proper value is used when computing reclaimable space

When Size was reverted to be equal to VirtualSize, the df command
formatter was not correctly updated to account for the change.

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>
(cherry picked from commit dcc1b4baf6d0eb068010d071bc44daf72b12cd4a)
Signed-off-by: Victor Vieux <vieux@docker.com>

cli/command/formatter/disk_usage.go

@@ -192,7 +192,10 @@ func (c *diskUsageImagesContext) Reclaimable() string {
 	c.AddHeader(reclaimableHeader)
 	for _, i := range c.images {
 		if i.Containers != 0 {
-			used += i.Size
+			if i.VirtualSize == -1 || i.SharedSize == -1 {
+				continue
+			}
+			used += i.VirtualSize - i.SharedSize
 		}
 	}
 

daemon/images.go

@@ -205,7 +205,7 @@ func (daemon *Daemon) Images(imageFilters filters.Args, all bool, withExtraAttrs
 	}
 
 	if withExtraAttrs {
-		// Get Shared and Unique sizes
+		// Get Shared sizes
 		for img, newImage := range imagesMap {
 			rootFS := *img.RootFS
 			rootFS.DiffIDs = nil